This invention relates to scraper rings for example for use in piston rod seals, particularly in low-speed diesel engines.
In many reciprocating engines and compressors the piston rod passes through a partition which separates the enclosed crankcase from either the surrounding atmosphere or a chamber containing or contaminated by the liquid or gas handled in the cylinder. Where the piston rod passes through the partition it is usual to fit some form of seal to prevent passage of fluid from one side of the partition to the other as the piston rod reciprocates. For example, it is essential to prevent oil which is adhering to the surface of the piston rod in the crankcase from passing through the seal as the piston rod moves outwards from the crankcase.
FIGS. 1 and 2 are isometric cutaway views of known forms of scraper ring which are essential components of such seals. These rings comprise a number of rigid or semi-rigid sections 1 held in contact with the piston rod 2 by a surrounding garter spring 3, the ring being supported in a close-fitting, parallel-sided groove indicated only in outline 4.
These conventional rings have been found to be not completely effective in removing all fluid from the piston rod, especially where the fluid is oil as in the crankcase, since even when the rubbing surface is initially made with sharp edges, as wear occurs the contact surface increases and the scraping action is reduced. Commonly, even though 6 or 8 rings may be fitted, the removal of surface oil is not completely effective.